Hot wire chemical vapor deposited multiphase silicon carbide (SiC) thin films at various filament temperatures

摘要

Influence of filament temperature (T_(Fil)) on the structural, morphology, optical and electrical properties of silicon carbide (SiC) films deposited by using hot wire chemical vapor deposition technique has been investigated. Characterization of these films by low angle XRD, Raman scattering, XPS and TEM revealed the multiphase structure SiC films consisting of 3C-SiC and graphide oxide embedded in amorphous matrix. FTIR spectroscopy analysis show an increase in Si-C, Si-H, and C-H bond densities and decrease in hydrogen content with increase in T_(Fil). The C-H bond density was found higher than the of Si-H and Si-C bond densities suggesting that H preferably get attached to C than Si. AFM investigations show decrease in rms surface roughness and grain size with increase in T_(Fil). SEM studies show that films deposited at low T_(Fil) has spherulites-like morphology while at high T_(Fil) has cauliflower-like structure. Band gap values ETauc and E_(04) increases from 1.76 to 2.10 eV and from 1.80 to 2.21 eV respectively, when T_(Fil) was increased from 1500 to 2000 ℃. These result show increase in band tail width (E_(04)-E_(Tauc)) of multiphase SiC films. Electrical properties revealed that σ_(Dark) increases from ～7.87 ×10~(-10) to 1.54 ×10~(-5) S/cm and E_(act) decreases from 0.67 to 0.41 eV, which implies possible increase in unintentional doping of oxygen or nitrogen due to improved crystallinity and Si-C bond density with increase in T_(Fil). The deposition rate for the films was found moderately high (21 ＜ r_(dep) ＜ 30 A/s) over the entire range of T_(Fil) studied.